A search engine typically receives input of a search query including one or more keywords. Then, the search engine locates search results (e.g., documents) containing the one or more keywords and provides a list of the search results, with a summary for each of the search results.
For example, the following is an example list of documents with summaries for the documents:
Document 1                Summary 1        
Document 2                Summary 2        
Typically, in a search engine, the summary of the search results is displayed based on how that summary is configured by a search provider (e.g., the company or entity providing the search engine).